Characterization of a urea optical sensor based on polypyrrole

A new optical sensor for urea determination is presented. It is based on th e enzymatic reaction with urease, which is first photoimmobilized with poly acrylamide onto a chemically polymerized polypyrrole (PPy) film. The main a dvantage of this sensor is that no indicator dye or pH indicator is needed, because PPy itself acts as the support and the indicator. These PPy films show an absorbance spectrum in the near IR range which is pH dependent. The variation of absorbance is thus directly related to the change of pH cause d during the enzymatic reaction, which is also dependent on the urea concen tration. The linear range of the sensor is from 0.06 to 1 M of urea, which is the common level of urea concentration found in blood and urine samples.